Dengue is a mosquito borne viral infection. It is caused by the bites of an infected female Aedes mosquito. The disease is widely distributed in almost 35 states/UTs in India.[1],[2] The North eastern (NE) region is also a vulnerable spot for carrying dengue virus infection. Out of the eight NE states, Assam and Arunachal Pradesh shared a significant numbers of dengue cases in every year.[3],[4],[5] Usually, the dengue positive cases are reported from largest metropolitan areas. As per previous records, a major outbreak of dengue has been taken place in Pasighat, East Siang district of Arunachal Pradesh.[4],[5] Beside this, large numbers of dengue cases have been also reported from Itanagar, the capital city of Arunachal Pradesh.[4],[5] In Assam, almost 70-80% of the dengue positive cases are reported from Kamrup district, the capital city of Assam.[6] Apart from Kamrup district, Lakhimpur district had also shared a major proportion of dengue cases in every year. The district had also shared a long interstate boundary with Arunachal Pradesh. Hence, the chances of getting dengue virus infection are more amongst the inhabitant of border areas, and thus there may be every possibility of spreading the dengue virus infection in the entire district. Keeping in mind, the present study was undertaken in Lakhimpur district to find the sociodemographic and epidemiological profile of dengue cases. The study has been undertaken in 2012 and continued up to 2015. All suspected dengue patients (as per the standard case definition of dengue) were included in the study. Two millilitres of blood samples was collected from all suspected dengue cases. Based on the onset of symptoms, all samples were tested for the detection of dengue viral non-structural 1 (NS1) antigen as well as dengue-specific immunoglobulin M (IgM) antibody using enzyme-linked immunosorbent assay (ELISA). The dengue ELISA positive cases were analysed in terms of time, place and person.

From 2012 to 2015, a total of 220 suspected dengue cases were screened for detection of dengue NS1 antigen as well as IgM antibody by ELISA method. The positivity rate for dengue infection was 47.27% (104/220). Out of 104 dengue positive cases, 25 samples had shown dengue NS1 positive, 15 cases with both dengue IgM and NS1 positive and other 64 cases had shown dengue IgM positive. The most common symptoms among dengue positive cases were fever (100%), followed by rash (63.46%), retro-orbital pain (60.58%), gum bleeding (58.65%) and headache (53.85%). In Lakhimpur district, the first dengue positive case was observed from Singia village of Laluk area under Bihpuria block in September 2012. The person carried dengue virus infection from Itanagar as he has visited to that place before the occurrence of symptoms.

Most of the dengue positive cases (47 nos) were reported in 2012 [Table 1]. After that, the cases of dengue were decreased surprisingly in 2013 (14 nos) and 2014 (3 nos). Again in 2015, a large number of dengue positive cases (40 nos) were reported from Lakhimpur district of Assam [Table 1]. The percentage positivity rate for dengue infection was 52.81% (47/89) in 2012, 82.35% (14/17) in 2013, 33.33% (3/9) in 2014 and 38.10% (40/105) in 2015. It was observed that about 35% (36/104) of dengue positive cases belonged to Lakhimpur urban areas [Table 1]. These finding has shown similarity with previous studies conducted in other areas.[2],[6] However, most of the studies nowadays revealed that dengue is no more in urban area infection, it is extending to rural areas also.[5] A significant number of dengue positive cases were also reported from Bihpuria as it is very near to Banderdewa town, the border of Arunachal Pradesh. Initially, dengue cases were reported from August and reached at peak during the month of October to November in every year. However, nowadays, dengue cases are observed from March onwards, and it followed year round cycle. Out of 104 dengue-positive patients, 32.69% (34/104) had shown travel history [Table 1]. However, 67.31% (70/104) cases had no travel history, and it indicates that dengue virus is circulating in the Aedes vectors prevalent in Lakhimpur, Assam. Amongst dengue positive cases, 76.92% (80/104) were male and 23.08% (24/104) belonged to female sex [Figure 1]. It has proven that males are found to be mostly affected as compared to female [Figure 1]. Several previous studies also supported that males are mostly at risk for carrying dengue infection as they are commonly engaged in outdoor activities.[6] A total of 46.15% (48/104) cases having dengue infection belonged to 21–30 years of age groups [Figure 1]. This finding is in accordance with many previous studies.[2],[6] Interestingly, the case fatality rate for dengue infection was found very low. The overall case fatality rate was 1.92%. Except two cases, all other patients having dengue virus infections were recovered after complete treatment, and no long-term squeal was observed in any of the patients during the follow-up study.

From the above study, it is concluded that prompt surveillance and regular awareness are the two major steps to be taken for early detection and prevention of dengue virus infection.

Acknowledgement

The authors is highly grateful to NIV Pune for providing Dengue IgM as well as NS1 kits. The author also wishes to express his heartfelt thanks to the Medical officers as well as the laboratory staff of North Lakhimpur Civil Hospital for helping in different steps during the study period.

India, Ministry of Health and Family Welfare. National Vector Borne Disease Control Programme. New Delhi: Directorate General of Health Services; 2016. Available from: http://www.nvbdcp.gov.in. [Last accessed on 2016 Jan 08].